Page:Popular Science Monthly Volume 31.djvu/336

322 spring to the organs of locomotion, become less supple and more attenuated, all of which contribute to the diminution of height. Carrying burdens on the head or shoulders leads to the same results. If to an excessive fatigue is added privation of sleep, organic reparation can not take place, and the causes which contribute to the diminution of stature accumulate and effect in the total a decrease which is relatively considerable. This fact is known to the tricksters who practice upon young men liable to military service so as to secure exemptions for them. If the men are only a few centimetres over the minimum standard of the service, these practitioners put them through a variety of fatiguing exercises, with carrying of burdens and privations, etc., till they succeed in reducing them below the minimum and causing them to be rejected on examination. The same influence of fatigue is also felt in ordinary life. The simple standing position, walking, and riding, all contribute to a reduction of the height. We are all taller in the morning than in the evening. Professor Martel made a communication on this subject to the German Surgical Congress held in Berlin in 1881, and presented a number of measurements, from which he concluded that men's statures varied perceptibly according to the hour of the day. The variation differs according to occupations, being less in the case of those which are sedentary.

The height of the adult continues stationary during mature age, but begins to diminish at about fifty-five or sixty years. The decrease is independent of the curvature of the vertebral column, and is exhibited upon robust men who still hold themselves up straight. It depends upon several causes, among which are a modification of the neck of the femur, flattening of the fatty cushions, with gradual ossification and decrease in thickness of the cartilages of the joints, particularly of those of the vertebral column.

Physical aptitudes are various according to stature; and we are able to draw important conclusions, particularly with reference to fitness for military service, from the determination of them. The bodily vivacity of small men is very much greater than that of large men. The man of small stature is nearly always quicker and more alert than a man who is tall and stout in proportion. This should be evident, for such a man has less weight to displace when he is moving, jumping or climbing; while it has been proved, by many experiments on animals, that the strength does not increase in proportion to the weight. Two horses weighing together three quarters of a ton can perform much more work, particularly if it be work involving rapidity, than a single horse having the same weight. A similar difference exists in the power of one large and stout man and two small men. The ratio of muscular energy to the pound of living weight is much greater with small or middling-sized men than with very large ones. The length of the limbs of the latter necessarily occasions an amplitude in his motions that makes execution slower. Length of limbs also contributes to a